BepiColombo-a planetary mission to Mercury Focal plane - - PowerPoint PPT Presentation

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MPI Project Review BepiColombo-a planetary mission to Mercury Focal plane instrumentation for the MIXS instrument Ringberg, 24.4.2007 Mercury as seen on 16.9.2004 1 Johannes Treis MPI Halbleiterlabor Institutions 2 Johannes Treis MPI

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MPI Project Review

BepiColombo-a planetary mission to Mercury

Focal plane instrumentation for the MIXS instrument Ringberg, 24.4.2007

Mercury as seen on 16.9.2004

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Institutions

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Contents

History of Mercury

  • bservation

The Planet Mercury BepiColombo The MIXS Instrument The FPA detector for

MIXS

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History of mercury observation

~ 3000 B.C: First known evidence of Mercury

  • bservations by sumerian priests in

mesopotamia. Planet known as Ubu-idim-gud-ud

Ziggurat of Ur

~ 1000 B.C: Detailed recordings of Mercury

  • bservations by babylonian

astronomers Planet known as Nabu or Nebu, referring to the babylonian messenger of gods, due to its swift movement and partial visibility.

Babylonian record

  • f Venus observation
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History of Mercury observation

~ 500 B.C: Greek astronomers give Mercury two names, Stilbon and Hermaon, depending whether it is visible in the morning or evening. Pythagoras

  • f Samos proposes that the two
  • bservations refer to a common

body, which is then called Hermes, after the greek messenger of gods, which is later identified with the roman god Mercury. In roman/greek mythology, Mercury is not

  • nly the messenger of gods and the god of

travellers, but also the god of merchants,

  • f crooks, liars and highwaymen.

Statue of Mercury by Giambologna (16th century, Florence)

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History of Mercury observation

Mercury in the staircase fresco by Gianbattista Tiepolo at the Wuerzburg residence (18th century).

Always displayed with the winged herlad’s staff wound by two snakes (caducaeus), winged sandals (talaria) and winged traveller’s hat (petasos), which inspired the astronomical symbol for Mercury:

Engl.: Merchant Commerce Mercury (Hg) Mercenary Wednesday

Rarely displayed alone, but either participating on assemblies of gods (mostly just arriving or leaving) or while delivering a message to a

  • recipient. Is also said to explain the

somewhat obscure messages of the gods to the mortals.

French: Merci Mercredi

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History of mercury observation

~ 1610: First telescopic observations of Mercury by Galileo Galilei 1631: The Mercury transit predicted by Johannes Kepler is observed by Pierre Gassendi, which is the first known observation of a planetary transit. 1639: Giovanni Zulpi discovers Mercury’s phases by telescopic observation, which proves that mercury orbits around the sun. 1737: John Bevis records the first his- torically observed Mercury occul- tation by Venus (28.5.1737) Next: 2133. 1800: First observation of surface features by Johann Schroeter. 1881: First surface map of mercury by Giovanni Schiaparelli.

Transit of Mercury, 7.5.2003

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History of Mercury observation

~ 1930: Mercury’s orbit irregularities are explained by GRT! ~ 1960: Discovery of anomalous tidal locking of orbital period to rotational period by radio observations 1965: Precise measurement of the planet’s orbital period. Guiseppe (Bepi) Colombo suggests an anomalous resonant tidal locking with a 3:2 ratio, i.e. Mercury rotates three times for every two revolutions round the sun. 1974: Until 1975, Mariner 10 passes Mer- cury 3 times. Flight plan suggested by Bepi Colombo included Venus- Swing-Bys. Unexpectedly, the revolu- tion period of Mariner 10 in this or- bit was exactly twice the revolution period of Mercury, so that only ~45 %

  • f mercury could be cartographed.

2000: Lucky imaging observations at Mount Wilson reveal details

  • f the uncartographed region. Observation with x-ray

satellites.

Mariner 10

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Future of Mercury observation

2004: Launch of the MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) probe by NASA. January 2008: First Mercury flyby October 2008: Second Mercury flyby September 2009: Third Mercury flyby March 2011: Entering Mercury orbit 1 year of mission lifetime Payload similar to BC, but simpler Pathfinder for BC

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Future of Mercury observation

2013: Launch of ESA’s mission

BepiColombo

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The planet Mercury

Sun (to scale) Mercury Venus Earth Radii to scale

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Mercury fact sheet

Orbital radius: 0.46 – 0.3 AU (70 – 46 x106 km) Radius: ~2440 km (34% of earth) Mass: 3.302×1023 kg Density: 5.43 g / cm3 Surface gravity: 3.7 m / s2 Rotation period: ~58 d Orbital period: ~85 d Axial tilt: 0.01° Incination: ~ 7 ° Albedo: 0.1 Atmosphere: Traces (H, He, O, K, Na, Ca) Surface temperatures: Equator North pole Mean: 70 °C

  • 70 °C

Min:

  • 170 °C
  • 190 °C

Max: 430 °C 107 °C Very small magnetic field (1% of earth) No moons Ice? Sulphur? Least well-known of the terrestrial planets

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Mercury surface

Moon-like surface, heavily cratered Basins (volcanism) Geologically inactive for a long time Weird morphologhic features Rupes Caloris basin Weird terrain

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Mercury mass

  • Terrestrial planet bulk composition

derives from equilibrium condensation from the solar nebula.

  • Not for Mercury – unpredicted

large uncompressed density

  • Large core – thin mantle – high Fe

content, observations imply low Fe.

  • Possibilities

1. Selective accretion

  • 2. Post Accretion

Vaporisation

  • 3. Massive Impact

Anomal density! Inhomogeneous mass distribution (spin-orbit resonance)!

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Mission targets

Origin and evolution of a planet close to the parent star Mercury as a planet: form, interior, structure, geology, composition and craters Detect traces of Mercury's vestigial atmosphere (exosphere): composition and dynamics Mercury's magnetized envelope (magnetosphere): structure and dynamics Origin of Mercury's magnetic field Test of Einstein's theory of general relativity

ESA cornerstone mission:

Giuseppe “Bepi“ Colombo (2.10.1920 – 20.2.1984)

Mercury surface as seem by Mariner 10

...collaboration with JAXA

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BepiColombo

Launch 2013 Platform: Soyuz Fregat B MCS: Mercury composite spacecraft 6 year long journey

Mercury composite spacecraft (MCS) Main challenges:

  • Thermal management
  • Power (!)
  • Radiation damage
  • Flight plan
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BepiColombo

Mercury transfer module (MTM) Mercury planetary

  • rbiter (MPO)

Mercury magnetospheric

  • rbiter (MMO)

Solar shield MCS exploded view

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BepiColombo

Scheduled arrival: 2019 On arrival: Deployment of MPO and MMO in their respective orbits 1 year of expected mission lifetime Possible prolongation by another year

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Mercury magnetospheric orbiter

Instruments:

MERMAG-M: Magnetometer MPPE: Mercury plasma particle experiment PWI: Plasma wave experiment MSASI: Mercury Sodium Atmospheric Spectral Imager MDM: Mercury dust monitor

zum Selberbasteln...

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Mercury planetary orbiter

Instruments:

BELA: Laser altimeter ISA Accelerometer MERMAG: Magnetometer MERTIS: Thermal infrared spectrometer MGNS: Gamma-ray and neutron spectrometer MIXS: x-ray spectrometer MORE: Radio science Ka-Band transponder PHEBUS: UV-Spectrometer SERENA: Neutral and Ionized particle analyzer SIMBIO: High resolution and stereo camera, visible and NIR spectrometer SIXS: Solar monitor

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The MIXS Instrument

  • Incident solar X-rays induce X-ray fluorescence

from the surface

  • Potentially an additional component induced by

incident protons and electrons

  • Precise intensity monitor needed!
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The MIXS Instrument

MIXS : Mercury Imaging X-ray Spectrometer Measure fluorescent X-rays from Mercury surface First few micron of depth are explored Solar Intensity X-ray Spectrometer (SIXS) provides reference information Detection of characteristic lines allows to determine element abundance Combination with IR measurements (MERTIS) yields mineralogy information Combination with soft γ-ray measurements (MGNS) yields element abundance in depth of ~1 m Average composition of Mercury’s crust Compositions of the major terrains Composition inside craters and crater structures Detection of iron globally and locally Correlation of surface Na, K and Ca with complementary measurements of exosphere probe of the surface-magnetosphere- exosphere system Sulphur at the poles and in the crust globally Chromium to Nickel ratio globally to constrain formation models

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MIXS

Two cameras Same focal plane detector Different optics Collimator (MIXS-C) and Telescope (MIXS-T) Telescope: MPC optics MIXS-C: Wide field imaging MIXS-T: Precise Mapping

MIXS-C FPA MIXS-T FPA

Footprint size: 14 km for periherm 52 km for apoherm

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MIXS-T Optics

Wolter type 1 geometry Conical approximation Iridium-coated lead silicate glass Angular resolution: ~ 1.7 arcmin FWHM Total FOV: 1° FWZM

Prototype

MCP optics (3 concentrical rings) MCP pore width: 20 μm Aperture: 21 cm Focal length: 1 m Effective area : 120 cm2 @ 1 keV 15 cm2 @ 10 keV

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MIXS-C Optics

Much simpler system Radially bent collimator with 8 degree fov Uses a 2x2 array of square pore square packed MCPs 64mm by 64mm aperture Detector distance 230mm

  • Collimator angular response
  • Collimator setup drawing
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FPA design

FRONT END ELECTRONICS FPA MAIN ASSEMBLY

Baffle Thermal strap Front bracket Sensor assembly

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Sensor assembly

MOUNTING FRAME THERMAL STRAP THERMAL STRAP SUPPORT CERAMICS SUPPORT BARS SENSOR ADAPTER SENSOR COOLING BLOCK

Radiation enters from backside Frame and cooling block are made of high-perfromance beryllium alloy Support bars of composite carbon fiber material Details need to be fixed

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Detector characteristics I

FOV & focal length: Minimum sensor area 1.75 x 1.75 cm2 Tradeoff between:

  • Spotsize in focal plane (~1 mm)
  • Oversampling PSF
  • Angular resolution
  • Number of readout channels
  • Resolution & charge splitting
  • Spectral purity

Resolution element size:

  • 0.2 km (periherm) and 0.8 km (apoherm) @ 300 μ pixel size
  • 0.3 km (periherm) and 1.3 km (apoherm) @ 500 μ pixel size

Sensor and pixel size

2 Alternatives: 64 x 64 pixels of 500 x 500 μm2 Sensor size: 3.2 x 3.2 cm2 96 x 96 pixels of 500 x 500 μm2 Sensor size 2.8 x 2.8 cm2

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Detector characteristics II

Energy range

6.40 keV 7.06 keV Fe K 2.31 keV 2.47 keV S K 5.90 keV 6.49 keV Mn K 2.02 keV 2.14 keV P K 5.41 keV 5.95 keV Cr K 1.74 keV 1.84 keV Si K 4.95 keV 5.43 keV V K 1.49 keV 1.55 keV Al K 4.51 keV 4.93 keV Ti K 1.25 keV 1.30 keV Mg K 3.69 keV 4.01 keV Ca K 1.04 keV 1.07 keV Na K 3.31 keV 3.59 keV K K 0.71 keV Fe L

Mercury key element emission lines

Energy range: < 0.5 keV to > 7.0 keV Detection of Fe using the Fe-L line

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Detector properties

Depends on annealing scenario

  • 40 ˚C (-45 ˚C)

Operation temperature

Detector plus FEs

≤ 2.5 W Power consumption

Depends on temperature

20 krad 3 x 1010 p/cm2 Radiation hardness

  • Ionizing
  • Non-Ionizing (10 MeV p)

Depends on FE speed

128 μs (192 μs) Time resolution

O.K.

≥ 80 % @ 500 eV QE

Depends on temperature

≤ 200 eV FWHM @ 1 keV Energy resolution

O.K.

300 x 300 mm2 Pixel size

O.K.

64 x 64 pixels Array dimension

O.K.

1.92 x 1.92 cm2 sensitive area Format

Comments Value Parameter Temperature most critical issue!

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Detector concept

FPA detector: DEPMOSFET Macropixel array

Monolithic Array of silicon drift chambers DEPMOSFET devices as readout nodes Scalable pixel size High QE due to high fill factor Bidirectional row-wise readout High readout speed Low power consumption

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X-type DEPMOSFET device

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Implementation: Pixel substructure

RB in P+ -driftring implants Polysilicon separators R1 in V_inner_substrate „readout node“

MIXS-T requirement: 300 x 300 μm2 pixels Can be implemented using 3 driftrings per pixel Driftring voltage cascade applied externally or generated by integrated resistive voltage divider

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Implementation: Central readout node

Place DEPFET device instead

  • f„conventional“ readout anode
  • r JFET

Charge integration capability for every cell

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Implementation: Matrix arrangement

Array of pixels on common bulk Common outermost drift ring (RB) Common thin homogeneous entrance window Common backside contact voltage Shared driftring voltages No insensitive inter-pixel gaps But: charge sharing between pixels possible

N-type high resistive bulk (common) Radiation entrance window (common) Ultra-thin p+ Pixel matrix

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Readout scheme

N S W E

2 Hemispheres (North and South) 32 x 64 Pixels each Read out by 1 CAMEX each Controlled by 2 Switchers each Readout speed: target 4 μs / row 6 μs / row might be necessary Depends on FE performance, temperature, capacitance...

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Detector overview

CAMEX CAMEX Switcher Switcher Switcher Switcher Thermal diodes Bias pads Voltage divider

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Entrance window configuration

Thermal reasons require external optical filter Incorporates also UV- filtering properties

Entrance window:

No UV-Filter As thin an aluminum layer as necessary (~30 nm) Required for entrance window radiation hardness QE larger than QE for 50 nm

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Front End ICs

Switcher ICs:

Vital control element of detector Present technology radiation tolerant Design not radiation tolerant

  • Esp. digital part

New radiation tolerant design is going to be submitted after first tests of PXD 05 devices Radiation tests required

CAMEX / VELA ICs:

Readout mode has been decided. Source follower is baseline in spite of intrinsic speed limit Design to be submitted ~02/07 Devices ready ~ 07/07 Speed is critical issue Radiation test to be done

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Radiation damage

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  • 40
  • 60
  • 80

200 400 600 800 1000

Energy resolution @ 1 keV (eV)

Operating temperature (deg. C) Pixel size (μm)

60.00 80.00 100.0 120.0 140.0 160.0 180.0 200.0 220.0 240.0 260.0 280.0 300.0

White Line: 200 eV

Full mission lifetime (full dose) Calculations based on experimental results both of ROSE and operating experience with XEUS devices

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  • 20
  • 40
  • 60
  • 80

200 400 600 800 1000

White Line: 200 eV

Operating temperature (deg. C) Pixel size (μm)

60.00 80.00 100.0 120.0 140.0 160.0 180.0 200.0 220.0 240.0 260.0 280.0 300.0

Energy resolution @ 1 keV (eV)

Mission halftime (half of the dose)

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  • 20
  • 40
  • 60
  • 80

200 400 600 800 1000

Operating temperature (deg. C) Pixel size (μm)

60.00 80.00 100.0 120.0 140.0 160.0 180.0 200.0 220.0 240.0 260.0 280.0 300.0

Energy resolution @ 1 keV (eV) White Line: 200 eV

Start of mission

Φtot = 3 x 1010 10 MeV protons /cm2

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Comparison: Annealing vs. no annealing

  • 30
  • 35
  • 40
  • 45
  • 50
  • 55
  • 60

100 150 200 250 300 350

White line: 200 eV requirement

Energy resolution FWHM @ 1 keV

Temperature (°C) Integration time (μs)

60 100 140 180 220 260 300

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  • 50
  • 55
  • 60

100 150 200 250 300 350

Temperature (°C) Integration time (μs)

60 100 140 180 220 260 300

Energy resolution FWHM @ 1 keV

White line: 200 eV requirement

4 μs / row 6 μs / row 4 μs / row 6 μs / row

Operating temperature of -41 ˚ C requires regular annealing cycle to remedy bulk damage and reduce leakage current Operation without annealing requires lower operation temperature, depending on speed ~ -46 ˚ C

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Detector response

Similar to lunar anorthosit Similar to lunar basalt

Calculations provided by J. Carpenter University of Leicester

Input flux Response for 200 eV @1 keV